pharmacology Flashcards
4 key concepts of pharmacokinetics?
ADME
Definitions:
Pharmacokinetics vs pharmacodynamics
Pharmacokinetics:
How the body acts on the drug (how its broken down etc)
Pharmacodynamics:
How the drug affects the body (uptake, distribution etc)
Define affinity
A measure of binding strength between an epitope (specific piece of the antigen) and an antibody binding site - the higher the affinity the better
describes how well a ligand BINDS to the receptor
Define efficacy
(Does an antagonist show efficacy?)
What on a graph shows this??
Maximum effect that can be achieved by drug
/ how well the ligand activates the receptor
No. An antagonist has affinity but zero efficacy. Bc antagonists don’t activate receptors!! An agonist however demonstrates affinity and efficacy.
Emax
Define potency
Value on graph?
What is the effect of fewer receptors on drug potency?
= drug strength/weakness aka how well a drug works
Or = Aka the strength of a drug at a particular dosage
Or = Or concentration/dosage required to produce 50% of the maximal effect
EC50
Fewer receptors will shift the dose-response curve to the RHS, this means drug potency will be reduced.
Would a drug with a lower EC50 have a lower or greater potency?
Greater potency.
partial vs full agonist?
A full agonist has high efficacy, producing a full response while occupying a relatively low proportion of receptors (they’ll also go up to 100%) on graphs
Vs
Apartial agonisthas lower efficacy than a full agonist. It produces sub-maximal activation even when occupying the total receptor population, therefore cannot produce the maximal response, irrespective of the concentration applied. Also (Partial agonists don’t have receptor reserve).
competitive vs non competitive inhibitors?
Can they reach max rate of reaction?
Competitive inhibitor = inhibitor may bind to an enzyme and block binding of the substrate, for example, by attaching to the active site.
B)—— Will decrease reaction rate but can be ‘out-competed’ if there is lots of substrate so can sill reach max reaction rate if enough substrate
Non-competitive inhibitor = inhibitor doesn’t block the substrate from binding to the active site. Instead, it attaches at allosteric site and blocks the enzyme from doing its job. This inhibition is said to be “noncompetitive” because the inhibitor and substrate can both be bound at the same time.
B)——-
Specificity vs selectivity?
Can aspirin be described as a selective drug?
Specificity:
Drugs with a specific action act directly on their receptor so not through another molecule
eg exenatide is specific for the GLP-1 receptor
Selectivity:
Acts on one target ad one target alone
(No compound is truly ever specific )
No. Aspirin is non-selective, it acts on COX1 and COX2.
Name 5 local routes of drug administration:
Name all routes of systemic routes of drug administration inc the 2 categories?
What route of drug administration has a bioavailability of 1?
- Topical - directly onto skin/mucosa
- intranasal
- Eye drops
- inhalation
- transdermal
Systemic -> enteral
- oral
- rectal
- sublingual
And -> parenteral
- IV
- IM
- SC
- inhalation
- transdermal
IV infusion, all the drug administered will go into the plasma.
What is the effect of an increase in pH on a weak acid?`
give an example of a weak acid
The weak acid will become more ionised.
aspirin
In terms of ionisation, what happens to Aspirin in the stomach?
What is the advantage of aspirin doing this in the stomach?
Explain what would happen to the bioavailability of aspirin if gastric pH increased.
Aspirin is a weak acid and so becomes less ionised in the stomach due to the low gastric pH.
This allows rapid non-ionic diffusion across the gut membrane into the plasma. Once in the plasma aspirin becomes more ionised again.
The bioavailability would decrease. Aspirin would be more ionised and so wouldn’t diffuse across the gut into the plasma as rapidly this would mean aspirin uptake would decrease.
bioavailability: define
formula?
The proportion of the drug that enters circulation and so can exert an effect on the body
= AUC oral / AUC IV x 100
area under the plasma drug concentration-time curve (AUC) reflects the actual body exposure to drug after administration of a dose of the drug and is expressed in mg*h/L.
What is the bioavailability of morphine taken orally?
50%.
What are the two ways by which drugs can be eliminated in the kidneys?
- Glomerular filtration.
2. Active secretion.
